This invention relates to a pressure reducing valve used to regulate the pressure of high-pressure gas such as hydrogen gas.
A pressure reducing valve includes an open-close valve arranged between a primary port and a secondary port. Opening and closing the open-close valve causes inflow of high-pressure gas through the primary port, and the gas reduced in pressure is supplied to outside through the secondary port.
As an example, Japanese Patent Application Publication No. 2011-108057 discloses a pressure reducing valve including a primary chamber communicating with a primary port, a secondary chamber communicating with a secondary port, and an open-close valve that makes switching between connecting and isolating the primary and secondary chambers. The open-close valve includes a valve stem, a valve seat fixing member, a valve seat member, a housing, a valve element, a valve spring, and a lid member. A valve seat placement part is provided in the housing. While the valve seat member is placed in the valve seat placement part, the valve seat fixing member is fitted to the housing by threads, thereby fixing the valve seat member to the valve seat placement part.
An upper part of the valve seat fixing member is arranged in the secondary chamber. The secondary chamber houses a piston and a piston spring. The piston is always biased by the piston spring toward the primary chamber. The valve stem is housed inside the valve seat fixing member. An upper end of the valve stem always abuts on a lower end of the piston. The lid member is fixed to the primary chamber of the housing. The valve element is supported by a lower end of the valve seat member and an upper end of the lid member inside the housing.
The valve element is always biased downstream by the biasing force of the valve spring arranged between the valve element and the lid member. An upper end of the valve element always abuts on a lower end of the valve stem. The valve element contacts or separates from the valve seat member in response to a difference between force acting from the secondary chamber toward the primary chamber and force acting from the primary chamber toward the secondary chamber, thereby switching between connecting and isolating the primary and secondary chambers.
In the case of the pressure reducing valve of Japanese Patent Application Publication No. 2011-108057, the valve seat fixing member fixing the valve seat member has a channel groove formed in an end surface facing the piston. The channel groove extends along the radial direction of the housing. Even if the valve element is fully open, specifically even if the piston abuts on the end surface of the valve seat fixing member, this channel groove ensures a channel for high-pressure gas to flow from the primary port toward the secondary port.
However, forming the channel groove in the valve seat fixing member reduces the strength of the end surface of the valve seat fixing member in an area where the channel groove is formed, compared to the case where the channel groove is not formed in the valve seat fixing member. Hence, when the piston contacts the valve seat fixing member to make the valve element open fully, the end surface of the valve seat fixing member in the area where the channel groove is formed might be worn easily. This might make wear debris mix in between the valve seat and the valve element, probably making it impossible to ensure hermeticity between the primary and secondary ports. This might be a cause for gas leakage to occur between the primary and secondary ports.